More than 30,000 Commonwealth Edison customers were without power late Wednesday night as a final line of storms marched toward the Chicago area.

Storms earlier in the day downed trees, dropped hail and torrential rain, and spawned what may have been at least one tornado in the far southwest suburbs.

Your Illinois Storm Photos

A ComEd spokesman said the utility's systems performed "very well" under the conditions: strong wind gusts and thousands of lightning strikes. At the peak of the outages, nearly 40,000 Chicago-area customers were knocked offline. Another 35,000 were without electricity in northwest Indiana, NIPSCO officials said.

Storms Cause Flooding, Street Closures

The National Weather Service reported at least one tornado on the ground, near Somonauk, during the evening rush hour. Large hailstones -- some half-dollar in size -- were reported in Aurora.

The storms delayed hundreds of people on planes and trains and created massive backups on area roadways. More than 360 flights were cancelled at O'Hare International Airport. For a time, all all inbound flights to O'Hare were kept at their origin. Midway International, to the south, saw another 50 cancellations.

Metra Rail temporarily suspended inbound and outbound trains on several lines due to the storms.

Lightning strikes were blamed for causing a massive house fire in Lemont. Another strike, to a home in Yorkville, caused extensive damage to a roof. No injuries were reported in either of those two incidents.

Most of the severe weather had moved out of the Chicago area by 1 a.m., when the last of the severe storm warnings expired.

Flash flooding was the biggest threat in the wake of the storms. Warnings were issued for several counties in both Illinois and Indiana.

Thursday will be a period for the area to dry out, with mostly sunny conditions and cooler inland temperatures in the low-to-mid 70s.